1. Field of the Invention
The present invention relates to a magnetic head suspension for supporting a magnetic head slider that reads and/or writes data from and to a recording medium such as a hard disk drive.
2. Related Art
A magnetic head suspension for supporting a magnetic head slider includes a supporting part that is connected to an actuator by way of a carriage arm, a load bending part that is supported by the supporting part and that generates a load for pressing the magnetic head slider toward a disk surface, a load beam part that is supported by the supporting part via the load bending part and transmits the load to the magnetic head slider, and a flexure portion that is supported by the load beam part and that supports the magnetic head slider.
More specifically, the supporting part has a boss portion, and is supported indirectly by the actuator with the boss portion being fixed to the carriage arm by swaging.
The boss portion is formed to have a cylindrical shape by being pressed. Accordingly, in a case where the supporting part integrally includes the boss portion and a distal end section for supporting the load bending part, it is difficult to keep the distal end section flat upon formation of the boss portion. The flatness of the distal end section of the supporting part cannot be kept, particularly, in a case where the distal end section is provided with a hole or a groove in a complex shape.
For the above reasons, the supporting part generally includes a first supporting member that has a flat plate shape and has the distal end section for supporting the load bending part, and a second supporting member that has the boss portion and is provided separately from the first supporting member. The second supporting member is joined by welding to the first supporting member such that the second supporting member is laminated on the upper surface of the first supporting member.
However, such a general supporting part has the following problems: an area of the supporting part at which the boss portion is positioned has an increased thickness in a through-thickness direction (in a z direction) perpendicular to the disk and the weight of the supporting part is increased.
There has been proposed a magnetic head suspension configured to solve the problems recited above such that a base plate, which has an outer periphery in a circular shape and is provided with a boss portion in a short cylindrical shape to be fixed by swaging to a carriage arm, is fitted in a hole provided in a proximal portion of a member forming a load beam (see Japanese Patent Publication No. 3340103 (hereinafter, referred to as Patent Document 1)).
The magnetic head suspension described in Patent Document 1 is useful in that, in comparison to the general supporting part, the thickness can be reduced at the area of the supporting part at which the boss portion is positioned as well as that the weight of the supporting part can be reduced.
However, in the magnetic head suspension described in Patent Document 1, the base plate is sized to have an outer diameter that closely fits in the hole provided in the proximal portion. As a result, there arise the following problems.
In a case where the outer diameter of the base plate is smaller than the inner diameter of the hole due to variation in size, the base plate easily fits in the hole, but insufficient joint strength between the base plate and the proximal portion lowers the resonant frequency of the magnetic head suspension.
To the contrary, in a case where the outer diameter of the base plate is close to the inner diameter of the hole due to variation in size, it is difficult or impossible for the base plate to fit in the hole. If the base plate is forcibly pressed into the hole, a load is applied to the proximal portion, and thus the flatness of the proximal portion is deteriorated.